There is a decolorable toner having a characteristic of decoloring the color at a certain temperature. In response to the growing social awareness of environmental protection in recent years, an image forming apparatus which is capable of printing with decolorable toner has been put to practical use. In a case of printing with decolorable toner, it is also considered that a mark for indicating the printing with decolorable toner, an image representing the decoloring times and the like are to be printed on a sheet together with the printing image.
In a case where the sheet on which the mark is printed is copied as a document, there is no doubt that the mark is also copied. However, the user does not want a copy of the mark through which the type of toner can be determined. That is, originally, the mark is the unnecessary information as the document. Thus, an image forming apparatus which can suppress the printing of the mark as needed is desired.